serial: 8250_aspeed_vuart: replace snprintf with sysfs_emit

coccinelle report:
./drivers/tty/serial/8250/8250_aspeed_vuart.c:85:8-16:
WARNING: use scnprintf or sprintf
./drivers/tty/serial/8250/8250_aspeed_vuart.c:174:8-16:
WARNING: use scnprintf or sprintf
./drivers/tty/serial/8250/8250_aspeed_vuart.c:127:8-16:
WARNING: use scnprintf or sprintf

Use sysfs_emit instead of scnprintf or sprintf makes more sense.
Reported-by: NZeal Robot <zealci@zte.com.cn>
Signed-off-by: NYang Guang <yang.guang5@zte.com.cn>
Signed-off-by: NDavid Yang <davidcomponentone@gmail.com>
Link: https://lore.kernel.org/r/fed40753603dac4d14b17970c88e6f5f936348c1.1644541843.git.yang.guang5@zte.com.cnSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_aspeed_vuart.c

@@ -82,7 +82,7 @@ static ssize_t lpc_address_show(struct device *dev,
 	addr = (aspeed_vuart_readb(vuart, ASPEED_VUART_ADDRH) << 8) |
 		(aspeed_vuart_readb(vuart, ASPEED_VUART_ADDRL));
 
-	return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);
+	return sysfs_emit(buf, "0x%x\n", addr);
 }
 
 static int aspeed_vuart_set_lpc_address(struct aspeed_vuart *vuart, u32 addr)
@@ -124,7 +124,7 @@ static ssize_t sirq_show(struct device *dev,
 	reg &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
 	reg >>= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
 
-	return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg);
+	return sysfs_emit(buf, "%u\n", reg);
 }
 
 static int aspeed_vuart_set_sirq(struct aspeed_vuart *vuart, u32 sirq)
@@ -171,7 +171,7 @@ static ssize_t sirq_polarity_show(struct device *dev,
 	reg = aspeed_vuart_readb(vuart, ASPEED_VUART_GCRA);
 	reg &= ASPEED_VUART_GCRA_HOST_SIRQ_POLARITY;
 
-	return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg ? 1 : 0);
+	return sysfs_emit(buf, "%u\n", reg ? 1 : 0);
 }
 
 static void aspeed_vuart_set_sirq_polarity(struct aspeed_vuart *vuart,